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Now *not static* msft functions hold and put hdev->msft_data. It prevents from potential and real use-after-free bugs. How msft is used after freed: [use] msft_do_close() msft = hdev->msft_data; if (!msft) ...(1) <- passed. return; mutex_lock(&msft->filter_lock); ...(4) <- used after freed. [free] msft_unregister() msft = hdev->msft_data; hdev->msft_data = NULL; ...(2) kfree(msft); ...(3) <- msft is freed. ================================================================== BUG: KASAN: slab-use-after-free in __mutex_lock_common kernel/locking/mutex.c:587 [inline] BUG: KASAN: slab-use-after-free in __mutex_lock+0x8f/0xc30 kernel/locking/mutex.c:752 Read of size 8 at addr ffff888106cbbca8 by task kworker/u5:2/309 CPU: 0 PID: 309 Comm: kworker/u5:2 Not tainted 6.9.0-rc5+ #5 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014 Workqueue: hci4 hci_error_reset Call Trace: __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0xcd/0x140 lib/dump_stack.c:114 print_address_description mm/kasan/report.c:377 [inline] print_report+0x191/0x560 mm/kasan/report.c:488 kasan_report+0xe2/0x120 mm/kasan/report.c:601 __asan_report_load8_noabort+0x18/0x20 mm/kasan/report_generic.c:381 __mutex_lock_common kernel/locking/mutex.c:587 [inline] __mutex_lock+0x8f/0xc30 kernel/locking/mutex.c:752 mutex_lock_nested+0x1f/0x30 kernel/locking/mutex.c:804 msft_do_close+0x292/0x700 net/bluetooth/msft.c:694 hci_dev_close_sync+0x906/0xf10 net/bluetooth/hci_sync.c:5168 hci_dev_do_close net/bluetooth/hci_core.c:554 [inline] hci_error_reset+0x152/0x410 net/bluetooth/hci_core.c:1091 process_one_work kernel/workqueue.c:3254 [inline] process_scheduled_works+0x90f/0x1530 kernel/workqueue.c:3335 worker_thread+0x926/0xe70 kernel/workqueue.c:3416 kthread+0x2e3/0x380 kernel/kthread.c:388 ret_from_fork+0x5c/0x90 arch/x86/kernel/process.c:147 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244 Allocated by task 7328: kasan_save_stack mm/kasan/common.c:47 [inline] kasan_save_track+0x30/0x70 mm/kasan/common.c:68 kasan_save_alloc_info+0x3c/0x50 mm/kasan/generic.c:565 poison_kmalloc_redzone mm/kasan/common.c:370 [inline] __kasan_kmalloc+0xa2/0xc0 mm/kasan/common.c:387 kasan_kmalloc include/linux/kasan.h:211 [inline] kmalloc_trace+0x20c/0x3e0 mm/slub.c:3997 kmalloc include/linux/slab.h:628 [inline] kzalloc include/linux/slab.h:749 [inline] msft_register+0x66/0x1d0 net/bluetooth/msft.c:760 hci_register_dev+0x85e/0x9a0 net/bluetooth/hci_core.c:2737 __vhci_create_device drivers/bluetooth/hci_vhci.c:438 [inline] vhci_create_device+0x390/0x720 drivers/bluetooth/hci_vhci.c:480 vhci_get_user drivers/bluetooth/hci_vhci.c:537 [inline] vhci_write+0x39b/0x460 drivers/bluetooth/hci_vhci.c:617 call_write_iter include/linux/fs.h:2110 [inline] new_sync_write fs/read_write.c:497 [inline] vfs_write+0x8eb/0xb50 fs/read_write.c:590 ksys_write+0x106/0x1f0 fs/read_write.c:643 __do_sys_write fs/read_write.c:655 [inline] __se_sys_write fs/read_write.c:652 [inline] __x64_sys_write+0x84/0xa0 fs/read_write.c:652 x64_sys_call+0x271a/0x2ce0 arch/x86/include/generated/asm/syscalls_64.h:2 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0x9c/0x130 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x76/0x7e Freed by task 7332: kasan_save_stack mm/kasan/common.c:47 [inline] kasan_save_track+0x30/0x70 mm/kasan/common.c:68 kasan_save_free_info+0x44/0x50 mm/kasan/generic.c:579 poison_slab_object+0x11a/0x190 mm/kasan/common.c:240 __kasan_slab_free+0x3b/0x60 mm/kasan/common.c:256 kasan_slab_free include/linux/kasan.h:184 [inline] slab_free_hook mm/slub.c:2106 [inline] slab_free mm/slub.c:4280 [inline] kfree+0x13c/0x330 mm/slub.c:4390 msft_unregister+0x9d/0x120 net/bluetooth/msft.c:785 hci_unregister_dev+0x1d9/0x520 net/bluetooth/hci_core.c:2771 vhci_release+0x8c/0xe0 drivers/bluetooth/hci_vhci.c:674 __fput+0x36f/0x750 fs/file_table.c:422 ____fput+0x1e/0x30 fs/file_table.c:450 task_work_run+0x1da/0x280 kernel/task_work.c:180 exit_task_work include/linux/task_work.h:38 [inline] do_exit+0x856/0x2210 kernel/exit.c:878 do_group_exit+0x201/0x2c0 kernel/exit.c:1027 get_signal+0x12ff/0x1380 kernel/signal.c:2911 arch_do_signal_or_restart+0x3b/0x650 arch/x86/kernel/signal.c:310 exit_to_user_mode_loop kernel/entry/common.c:111 [inline] exit_to_user_mode_prepare include/linux/entry-common.h:328 [inline] __syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline] syscall_exit_to_user_mode+0xcc/0x2a0 kernel/entry/common.c:218 do_syscall_64+0xa8/0x130 arch/x86/entry/common.c:89 entry_SYSCALL_64_after_hwframe+0x76/0x7e The buggy address belongs to the object at ffff888106cbbc00 which belongs to the cache kmalloc-256 of size 256 The buggy address is located 168 bytes inside of freed 256-byte region [ffff888106cbbc00, ffff888106cbbd00) The buggy address belongs to the physical page: page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x106cba head: order:1 entire_mapcount:0 nr_pages_mapped:0 pincount:0 flags: 0x17ffffe0000840(slab|head|node=0|zone=2|lastcpupid=0x3fffff) page_type: 0xffffffff() raw: 0017ffffe0000840 ffff888100042040 ffffea00042de590 ffffea00041b3e10 raw: 0000000000000000 00000000000a000a 00000001ffffffff 0000000000000000 head: 0017ffffe0000840 ffff888100042040 ffffea00042de590 ffffea00041b3e10 head: 0000000000000000 00000000000a000a 00000001ffffffff 0000000000000000 head: 0017ffffe0000001 ffffea00041b2e81 dead000000000122 00000000ffffffff head: 0000000200000000 0000000000000000 00000000ffffffff 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffff888106cbbb80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff888106cbbc00: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >ffff888106cbbc80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff888106cbbd00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff888106cbbd80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ================================================================== Fixes: 9e14606d8f38 ("Bluetooth: disable advertisement filters during suspend") Signed-off-by: Sungwoo Kim --- v2: Move BT_DBG after null checking in msft_data_hold_unless_zero() net/bluetooth/msft.c | 124 ++++++++++++++++++++++++++++++++++--------- 1 file changed, 99 insertions(+), 25 deletions(-) diff --git a/net/bluetooth/msft.c b/net/bluetooth/msft.c index 9612c5d1b..1f79e7980 100644 --- a/net/bluetooth/msft.c +++ b/net/bluetooth/msft.c @@ -132,10 +132,45 @@ struct msft_data { __u8 filter_enabled; /* To synchronize add/remove address filter and monitor device event.*/ struct mutex filter_lock; + struct kref kref; }; +static void msft_data_free(struct kref *kref); + +static struct msft_data *msft_data_hold_unless_zero(struct msft_data *msft) +{ + if (!msft) + return NULL; + + BT_DBG("msft %p orig refcnt %u", msft, kref_read(&msft->kref)); + + if (!kref_get_unless_zero(&msft->kref)) + return NULL; + + return msft; +} + +static void msft_data_put(struct msft_data *msft) +{ + BT_DBG("msft %p orig refcnt %u", msft, kref_read(&msft->kref)); + + kref_put(&msft->kref, msft_data_free); +} + +static void msft_data_free(struct kref *kref) +{ + struct msft_data *msft = container_of(kref, struct msft_data, kref); + + BT_DBG("msft %p", msft); + + kfree(msft->evt_prefix); + mutex_destroy(&msft->filter_lock); + kfree(msft); +} + bool msft_monitor_supported(struct hci_dev *hdev) { + /* msft_get_features() holds and put hdev->msft_data */ return !!(msft_get_features(hdev) & MSFT_FEATURE_MASK_LE_ADV_MONITOR); } @@ -449,12 +484,17 @@ static int msft_remove_monitor_sync(struct hci_dev *hdev, /* This function requires the caller holds hci_req_sync_lock */ int msft_suspend_sync(struct hci_dev *hdev) { - struct msft_data *msft = hdev->msft_data; + struct msft_data *msft; struct adv_monitor *monitor; int handle = 0; - if (!msft || !msft_monitor_supported(hdev)) + msft = msft_data_hold_unless_zero(hdev->msft_data); + if (!msft) return 0; + if (!msft_monitor_supported(hdev)) { + msft_data_put(msft); + return 0; + } msft->suspending = true; @@ -471,6 +511,7 @@ int msft_suspend_sync(struct hci_dev *hdev) /* All monitors have been removed */ msft->suspending = false; + msft_data_put(msft); return 0; } @@ -608,11 +649,17 @@ static void reregister_monitor(struct hci_dev *hdev) /* This function requires the caller holds hci_req_sync_lock */ int msft_resume_sync(struct hci_dev *hdev) { - struct msft_data *msft = hdev->msft_data; + struct msft_data *msft; - if (!msft || !msft_monitor_supported(hdev)) + msft = msft_data_hold_unless_zero(hdev->msft_data); + if (!msft) return 0; + if (!msft_monitor_supported(hdev)) { + msft_data_put(msft); + return 0; + } + hci_dev_lock(hdev); /* Clear already tracked devices on resume. Once the monitors are @@ -625,17 +672,19 @@ int msft_resume_sync(struct hci_dev *hdev) reregister_monitor(hdev); + msft_data_put(msft); return 0; } /* This function requires the caller holds hci_req_sync_lock */ void msft_do_open(struct hci_dev *hdev) { - struct msft_data *msft = hdev->msft_data; + struct msft_data *msft; if (hdev->msft_opcode == HCI_OP_NOP) return; + msft = msft_data_hold_unless_zero(hdev->msft_data); if (!msft) { bt_dev_err(hdev, "MSFT extension not registered"); return; @@ -650,8 +699,7 @@ void msft_do_open(struct hci_dev *hdev) msft->features = 0; if (!read_supported_features(hdev, msft)) { - hdev->msft_data = NULL; - kfree(msft); + msft_data_put(msft); return; } @@ -663,15 +711,17 @@ void msft_do_open(struct hci_dev *hdev) */ reregister_monitor(hdev); } + msft_data_put(msft); } void msft_do_close(struct hci_dev *hdev) { - struct msft_data *msft = hdev->msft_data; + struct msft_data *msft; struct msft_monitor_advertisement_handle_data *handle_data, *tmp; struct msft_monitor_addr_filter_data *address_filter, *n; struct adv_monitor *monitor; + msft = msft_data_hold_unless_zero(hdev->msft_data); if (!msft) return; @@ -705,6 +755,8 @@ void msft_do_close(struct hci_dev *hdev) hdev->advmon_pend_notify = false; msft_monitor_device_del(hdev, 0, NULL, 0, true); + msft_data_put(msft); + hci_dev_unlock(hdev); } @@ -767,6 +819,7 @@ void msft_register(struct hci_dev *hdev) INIT_LIST_HEAD(&msft->address_filters); hdev->msft_data = msft; mutex_init(&msft->filter_lock); + kref_init(&msft->kref); } void msft_unregister(struct hci_dev *hdev) @@ -779,10 +832,7 @@ void msft_unregister(struct hci_dev *hdev) bt_dev_dbg(hdev, "Unregister MSFT extension"); hdev->msft_data = NULL; - - kfree(msft->evt_prefix); - mutex_destroy(&msft->filter_lock); - kfree(msft); + msft_data_put(msft); } /* This function requires the caller holds hdev->lock */ @@ -1068,10 +1118,11 @@ static void msft_monitor_device_evt(struct hci_dev *hdev, struct sk_buff *skb) void msft_vendor_evt(struct hci_dev *hdev, void *data, struct sk_buff *skb) { - struct msft_data *msft = hdev->msft_data; + struct msft_data *msft; u8 *evt_prefix; u8 *evt; + msft = msft_data_hold_unless_zero(hdev->msft_data); if (!msft) return; @@ -1081,21 +1132,21 @@ void msft_vendor_evt(struct hci_dev *hdev, void *data, struct sk_buff *skb) if (msft->evt_prefix_len > 0) { evt_prefix = msft_skb_pull(hdev, skb, 0, msft->evt_prefix_len); if (!evt_prefix) - return; + goto done; if (memcmp(evt_prefix, msft->evt_prefix, msft->evt_prefix_len)) - return; + goto done; } /* Every event starts at least with an event code and the rest of * the data is variable and depends on the event code. */ if (skb->len < 1) - return; + goto done; evt = msft_skb_pull(hdev, skb, 0, sizeof(*evt)); if (!evt) - return; + goto done; hci_dev_lock(hdev); @@ -1112,13 +1163,24 @@ void msft_vendor_evt(struct hci_dev *hdev, void *data, struct sk_buff *skb) } hci_dev_unlock(hdev); + +done: + msft_data_put(msft); } __u64 msft_get_features(struct hci_dev *hdev) { - struct msft_data *msft = hdev->msft_data; + struct msft_data *msft; + unsigned long long features; + + msft = msft_data_hold_unless_zero(hdev->msft_data); + if (!msft) + return 0; + + features = msft->features; - return msft ? msft->features : 0; + msft_data_put(msft); + return features; } static void msft_le_set_advertisement_filter_enable_cb(struct hci_dev *hdev, @@ -1152,37 +1214,48 @@ static void msft_le_set_advertisement_filter_enable_cb(struct hci_dev *hdev, /* This function requires the caller holds hci_req_sync_lock */ int msft_add_monitor_pattern(struct hci_dev *hdev, struct adv_monitor *monitor) { - struct msft_data *msft = hdev->msft_data; + struct msft_data *msft; + int err; + msft = msft_data_hold_unless_zero(hdev->msft_data); if (!msft) return -EOPNOTSUPP; - if (msft->resuming || msft->suspending) + if (msft->resuming || msft->suspending) { + msft_data_put(msft); return -EBUSY; + } - return msft_add_monitor_sync(hdev, monitor); + err = msft_add_monitor_sync(hdev, monitor); + msft_data_put(msft); + return err; } /* This function requires the caller holds hci_req_sync_lock */ int msft_remove_monitor(struct hci_dev *hdev, struct adv_monitor *monitor) { - struct msft_data *msft = hdev->msft_data; + struct msft_data *msft; + int err; + msft = msft_data_hold_unless_zero(hdev->msft_data); if (!msft) return -EOPNOTSUPP; if (msft->resuming || msft->suspending) return -EBUSY; - return msft_remove_monitor_sync(hdev, monitor); + err = msft_remove_monitor_sync(hdev, monitor); + msft_data_put(msft); + return err; } int msft_set_filter_enable(struct hci_dev *hdev, bool enable) { struct msft_cp_le_set_advertisement_filter_enable cp; - struct msft_data *msft = hdev->msft_data; + struct msft_data *msft; int err; + msft = msft_data_hold_unless_zero(hdev->msft_data); if (!msft) return -EOPNOTSUPP; @@ -1193,6 +1266,7 @@ int msft_set_filter_enable(struct hci_dev *hdev, bool enable) msft_le_set_advertisement_filter_enable_cb(hdev, &cp, err); + msft_data_put(msft); return 0; }